If your nsdh has been living a secret life of adulterous relationships for the past few years, I daresay he could have written the book.
In an age where homsexuality was a crime, it's easy to understand why TE Lawrence, Tchaikovsky, and countless other gay men kept that aspect of their lives under wraps, as it were.
But sociopaths/psychopaths and others with disordered personalities have more sinister reasons for maintaining secret lives.
The danger of men like your nsdh reading books like this is they may seize upon certain words or alleged 'facts' to validate the choice they made to deceive others.
When he's finished the tome, I trust you will be able to disabuse him of any notion that his choice was, or is, in any way acceptable to right-minded or right-thinking people.
No matter what fancy pyschological terms are used to explain such behaviour, he needs to know that there can be no justification for him being a deceitful, dishonest, duplicitious toe-rag.
FWIW, the only use this book can be to you is as a weapon to brain him with 